Electric organ



July 1, 1958 E. SCHREIBER 2,841,043

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ELECTRIC oRGAN v Filed Jan. l, 1956 s sheets-sheet s ATTORNEY UnitedStift-.tes Patent Otlce 2,841,043 Patented July 1, 1958 ELECTRIC QRGANErnst Schreiber, Berlin, Germany, assigner to Vel) Werk furFernmeldewesen, Berlin-Oberschoenr/eide, Germany Application January 31,1956, Serial No. 562,528 Claims. (Cl. 84-1.13)

The present invention relates to electric musical instruments having akeyboard, and more particularly to electric organs having several stops.

It is an object of the present invention to reduce the number of tubesused in the controlling members of the organ.

It is another object of the present invention to improve the organs froman economical point of view.

lt is a further object of the present invention to improve an organ inthe operation thereof.

It is still another object of the present invention to reduce the oorspace required by the tubes and/or the switching elements of an electricorgan.

Other objects and advantages of the present invention l will becomeapparent from the following detailed description thereof in connectionwith the accompanying drawings showing, by way of example, an embodimentof an organ according to the present invention.

In the drawings:

Fig. l is a wiring diagram of an electric organ according to the presentinvention,

Fig. la is a wiring diagram of a modication of Fig. l,

Fig. 2 is a simpliried diagram of one stage shown in Fig. 1, and la andFig. 3 is a diagram for the explanation of the operation of the electricorgan shown in Figs. 1 and 2.

Referring now to the drawings and first to Fig. 1 a key system is showncomprising a plurality of, for instance seven, stop positions, and moreespecially for the 16', the 8', the 4', the 2%', the 2', the 1?/5 andthe l' positions. The key system includes seven bus bars 1-7 associated,respectively, with the seven register positions 16 to 1'. Each of thebus bars 1-7 is associated with sixty-one tone generators correspondingto the number of keys of the manual and thirty tone generatorscorresponding to the number o f keys of the pedal. In Fig. l single tonegenerators 8-14 are shown for each bus bar 1 7, respectively. Thevoltages supplied by the tone generators 8-14 are reduced topredetermined voltages by the voltage dividers or potentiometers 16, 17/18, 19/20, 21/22, 23/24, 25/26, and 27/28, respectively.

The bus bars 1-7 are connected, respectively, with diode rectifyingelements 29-35 for the control of the tones.A These seven rectiers 29-35are arranged in the circuit of a control tube 36 having a grid 36g towhich is imparted a high negative bias over a resistor 38 so that thetube 36 is blocked. The resistor 38 is connected in series with avoltage source or battery 38b connected with the cathode 36e of the tube36. A second resistor 39 and a switch 37 connected in series thereto areconnected in parallel to the resistor 38 and the battery 38b and reducethe grid bias upon closing the switch 37 so far that the normal workingpoint of the characteristic of the tube 36 is shifted. A capacitor 40 isconnected in parallel with the resistor 38 and the battery 38b so thatthe same has also the potential of the grid bias. The capacitor 40 hasthe effect that the grid bias is not reduced suddenly but in a period oftime corresponding to the time constant of the transient circuit formedby the resistor 39 and the capacitor 40., A capacitor 41 connected withthe anode 36a of the tube 36 short-circuits the seven tone frequenciesagainst the tube 36.

The direct current output of the diode rectiers 29-35 is controlled overdecoupling resistors 42-48 by the tube 36 according to the position ofthe switch 37. Furthermore, second diode rectifying elements 49-53 areinserted, for instance, in the bus bars 1 5. Capacitors 54-58 areconnected, respectively, between the junctions of the resistors 42-46and the rectiers 49-53 and the cathode 36C of the tube 36, their purposebeing a prolongation of the onset of sound or an additional delaying ofthe onset impulse as more fully described hereinafter.

The operation of this device is as follows, reference being made toFigs. 2 and 3 of the drawings, Fig. 2 showing only the bus bar 1 for the16' stop position, the circuit elements 49 and 54 being omitted. ln Fig.3 the resistance values of the rectifier element 29 are plotted againstthe voltage; this ligure shows the resistance characteristic K of therectifying element 29 in dependence on the voltage applied to therectifying element, and more particularly in the low resistancedirection corresponding to positive values of the voltage, and in thenegative direction corresponding to negative values of the voltage.

The operation of the circuit shown in Fig. 2 is based on the resistancecharacteristic shown in Fig. 3. The resistor 16 of the voltage divider15, 16 should have a value of, for instance l megohm. The rectifierelement 29 connected in parallel to the resistor 16 is controlled bymeans of the tube 36.

When the contact 37 is closed so that the tube 36 reaches the normalworking point of its characteristic at a reduced grid bias, an anodecurrent will flow through the tube 36 over the correspondingly poledrectier 29 and the decoupling resistor 42. As shown in Fig. 3, therectiiier element 29 has in the current carrying direction only arelatively low resistance value amounting to, for instance, ohms whichis connected in parallel with the resistor 16 having an assumed value ofl megohm. Thus it will be seen that the resulting resistance value ofthe circuit elements 16 and 29 is below 150 ohms so that the voltagedivider ratio between the high ohmic resistor 15 and the resultantresistance is shifted so as to reduce by short circuiting the voltage ofthe tone generator 8 on the bus bar 1 practically to zero. If now thecontact 37 is opened by depressing a key of the manual or pedal (notshown), the full negative grid bias is imparted to the grid 36g of thetube 36. ln consequence thereof the tube 36 is absolutely blocked sothat no anode current flows through this tube. Thus the rectifierelement 29 is not current carrying in this position of the circuitelements.

As will be seen from the resistance characteristic K shown in Fig. 3 ofthe drawings the rectifying element 29 has in this case a resistancevalue amounting to about SO kiloohms. This value is connected inparallel to the resistor 16 and yields a resultant resistance ofapproximately 333 kiloohms. This voltage divider ratio between theresistor 15 and the resultant resistance of 333 kiloohms has the electthat the desired alternating voltage of the tone generator 8 appears onthe bus bar l.. The tube 36 is now connected in parallel with theparallel conibination of the resistor 16 and the rectiiying element 29.ln order to prevent a short circuit by this parallel connection thedecoupling resistor 42 is inserted in the line to the anode 36a of thetube 36 and is sufciently highohmic to prevent a short circuit.

In order to prevent at the keying of a tone the sound potential fromsuddenly increasing to its final value or conversely decreasing from itslinal value to zero, the time constant members 38-40 including theresistors 38, 39 and the capacitor 4@ are provided so that the openingand closing of the tube 36 is effected in predetermined intervals oftime.Y I

The switching7 contact 37 is a rest contact which is in closing positionwhen no key of the manual or pedal (not shown) is depressed. When thecontact 37 is opened at the depressing of a key, the tube 36 is blockedas described hereinabove and thus the anode current thereof isinterrupted. At the same time the rectifying element 29 attains theblocking resistance thereof of about 500 kiloohms. When the soundvoltage at the bus bar 1 amounts to, for instance, l volt the positivehalf wave of the sound voltage curve falls in the range of thedecreasing branch of the resistance characteristic K shown in Fig. 3.VThus a voltage loss andan unbearable distortion of the sound voltagecurve occurs. In order to prevent this, one end I6 of the resistor I6 isconnected to the full potential of the anode battery B whereas thevoltage connection 29 of the rectifying element 29 is connected to anintermediate terminal 29" having a somewhat lower potential. Theoperation of this arrangement is as follows:

When the tube 36 is open, that is carrying a current, a circuit isestablished over the rectifier 29 including the cathode 36C of the tube36, the anode 36a of the same, the resistor 42, the rectiiier 29, theintermediate terminal 29", vthe batteryB and back to the cathode 36e.Although the resistor I6 being connected in parallel to the rectier 29has a Vsomewhat'higher D. C. potential, practically no current will flowthrough the resistor 16 because at the assumed resistance value of lmegohm the voltage drop across the resistor i6 will be very high incomparison to the voltage drop across the rectifier 29 having aresistance value of 150 ohms in current carrying condition.

However, conditions are changed when the tube 36 is shifted into theblocking condition thereof by depressing a key of the manual vor pedal(not shown). In this condition no current will flow through the rectier29 so that the increased direct potential across the resistor 16 isapplied to the end 29a of the rectifying element 29 turning toward thebus bar l. This is practically equivalent to a further shifting of theresistance characteristic K of the rectifying element 29 into theblocking range, that is into the negative range of the resistancecharacteristic. In other words, the tone voltage present on the bus barVl cannot shift operation of the rectifier 29 into the falling range ofthe characteristic. Thereby a distortion of the tone voltage and thus anundefined change of the timbre thereof is avoided.

ASince in the circuit according to the present invention a singlecontrol tube 36 serves for the control of the rectifying elements 229-35of a plurality of stop positions, all the stop positions are associatedwith the same onset and decay times. However, this does not correspondto the requirements of a synthetic imitation of transients since thedeeper stop positions have a longer onset time than the higher stoppositions. In order to satisfy these conditions also in an arrangementaccording to the invention the deeper stop positions, for instance thoseassociated with the bus bars 1 5, are provided with capacitors 54-58,respectively, which are connected to the bus bars 1 5. If the contactswitch 37 is in closed position an anode current will ow through thecontrol tube 36 over the rectier element 29 and the resistor 42 acrosswhich a considerable voltage drop will develop which has the eifect thatthe potential ofthe capacitor 54 is considerably smaller than thepotential applied to the rectifying element 29. When by a depression ofthe key the switch contact 37 is opened, the tube 36 is blocked within aperiod of time depending on the time constant of the RC-members 33, 4t?.This time constant is chosen so that it corresponds to the period of theonset transient of the highest stop positions, that is to the 1 and 1%stop. In

order to obtaina longer onset period in the deeper stop positions, thatis in the 16 to 2' stops, care should be taken that after the blockingof the control tube 36 a certain rectified current may flow in therectiier elements 29-33. This is accomplished by the capacitors 54 58 inconnection with the decoupling resistors 42 46. As mentionedhereinabove, a considerable voltage drop is encountered acrossthedecoupling resistors 42 46. If now the control tube 36 is blocked, acurrent will flow through the resistor 42 for ya certain period of timeso as to charge the capacitor 54 with the potential prevailing acrossthe rectifier 29. The period of time taken by this charging depends onthe time constant characterizing the resistor 42 and the capacitor 54.

In order to maintain these conditions at the anode 36a of the tube 36when the seven stop positions are switched on together, rectifyingelements 49-53 are provided in the lines of the corresponding bus bars 15. In this way it is accomplished that the individual time constantmembers do not iniluence one another.

Figure la shows an arrangement which is the same as that of Figure l,except that instead of the rectifier elements 49-53 decoupling resistors49 to 53 are used.

While I have described hereinabove a preferred embodiment of an electricorgan, it will be understood that many changes and modificationsthereof, and substitutions of equivalents are to be considered asfalling Within the scope of the appended claims.

I claim: t 1. In an electric musical instrument having a plurality Vofkeys each associated with a respective multi-position stop; a pluralityof tone control arrangementstfor saidkeys, respectively, each controlarrangement comprising a single electronic vacuum tube for allassociated stop positions, a resistance-capacitance transient circuitfor ap plying a bias voltage to said tube, switch means in said circuitand `operable when closed to reduce the resistance of said circuit andthus the bias on said tube to avalue rendering said tube conductive, andoperable when open to increase the resistance of said circuit and thusthe bias on said tube to a value rendering said tube nonconductive, saidswitch means being normally closed when the respective key isinoperative and being arranged to be opened by said respective key whenthe same is operative, and a plurality of grounded diodeV rectiiiers,

one for each stop position, arranged in parallel with one another :andconnected across said tube, whereby when said switch means is closed andsaid tube is reni dered conductive said rectiers are operated in theirvoltage-transmission ranges and tone voltages applied to said rectiersare shorted to ground via said rectiiers, while when said tube isrendered nonconductive due to opening of said switch means by saidrespective key said rectiers are operated in their voltage-blockingranges and said tone voltages are not shorted to ground and may be takenoff across said rectiiers vfor subsequent amplificationY andtransformation into sounds.

2. In an instrument according to claim l; each control arrangementfurther comprising a plurality of decoupling resistors each connectedbetween the output terminal` of a respective one of said rectiiers andthe plate of said tube, a plurality of bus bars connected, respectively,to the junctions between said decoupling resistors and said outputterminals of said rectiers, a plurality of voltage dividers arranged inparallel withV saidrectitiers and each having first and secondterminals, said rst terminals being connected, respectively, to said busbars, and a source of D.C. potential .connected to said second terminalsand to the cathode of said tube, the input terminals of said rectitiersbeing connected to said source of potential in such a manner` as to besubjected to a lesser potential than said voltage dividers.

3. In an instrument according to claim 2; the resistansie.andcapacitance values of said transient circuit being so chosen as toimpart to the latter a predetermined time constant corresponding to theattack rate of the tones in the highest stop positions, each controlarrangement further comprising a plurality of capacitors connected tosaid cathode of said tube and to the junctions between said plate ofsaid tube and those of said decoupling resistors associated with thelower stop positions, said capacitors and decoupling resistorsconstituting additional transient circuits for retarding the attack rateof the tones in said lower stop positions.

4. In an instrument according to claim 3; each control arrangementfurther comprising a plurality of additional diode rcctiers having theiroutput terminals connected to said plate of said tube and their inputterminals connected to the junctions between said capacitors and saiddecoupling resistors associated with said lower stop positions,

5. In an electric organ having tone voltage generar tor means and aplurality of keys each associated with some of said tone genrator meansand with a respective multi-position stop; a plurality of tone controlarrangements for said keys, respectively, each control arrangementcomprising a vacuum tube provided with a plate, a grid and a cathode,first resistance means and bias voltage means' connected in series withone another between said grid and cathode for biasing said tube tocut-off, capacitance means connected in parallel with said rstresistance means and said bias voltage means, second resistance meansarranged in parallel with said rst resistance means and said biasvoltage means,l switch means for connecting said second resistance meansto and for disconnecting the same from said first resistance means, saidswitch means being normally closed so as to reduce the bias' voltageapplied to said grid to a value rendering said tube conductive, saidswitch means being arranged to be opened by the respective key tomaximize said bias voltage applied to said grid so as to render saidtube nonconductive, a plurality of bus bars for conducting tonevoltages, a plurality of decoupling resistors connecting said bus bars,respectively, with said plate, a plurality of resistive voltage dividersarranged in parallel, a rst end point of each voltage divider beingconnected to said cathode, a second end point of each voltage dividerbeing connected to corresponding tone voltage generator means, anintermediate point of each voltage divider being connected to thejunction between the associated bus bar and the corresponding decouplingresistor, and a plurality of diode rectiiiers arranged in parallel withone another and connected with their output terminals to said junctionsbetween said bus bars and said decoupling resistors, and connected withtheir input terminals to ground and to the junction between said secondcnd points of said voltage dividers and said cathode, whereby when saidtube is rendered conductive upon closing of said switch means saidrectiters are operated in their voltage-transmission ranges and saidtone voltages are shorted to ground via said rectitiers, while when saidtube is rendered nonconductive due to opening of said switch means bysaid respective key said rectiiiers are operated in theirvoltage-blocking ranges and said tone voltages are not shorted to groundand are conducted away by said bus bars for subsequent amplification andtransformation into sounds.

References Cited in the file of this patent UNITED STATES PATENTS2,466,959 Moore Apr. l2, 1949 2,483,823 George Oct. 4, 1949 2,535,303Lewis Dec. 26, 1950 2,695,386 Schmidt Nov. 23, 1954

